Downflow denitrification system

Abstract

In general, the present invention is directed to systems for treating water or wastewater. In accordance with some embodiments of the present invention, the system may utilize a vessel with a plurality of filter beds, at least one inlet, and at least one outlet, and the system may include: a first filtration bed comprising a first granular and/or angular media, the first media having a high surface area and configured for biological and physical treatment of the water or wastewater; a second filtration bed including a second granular and/or angular media, the second media having a lower surface area than the first media; wherein the water or wastewater enters the vessel via the at least one inlet, flows through the first filtration bed and the second filtration bed, and exits the vessel through the at least one outlet.

What is claimed is: 
     
       1. A system for the removal of nitrates from water or wastewater, the system utilizing an anoxic vessel with a plurality of filter beds, at least one inlet, and at least one outlet, the system comprising:
 a first filtration bed comprising a first granular and/or angular media, the first granular and/or angular media having a first amount of surface area per volume of the first filtration media, the surface area of the first filtration media configured for biological and physical treatment of the water or wastewater; 
 a second filtration bed having a depth no less than 10% and no more than 50% the depth of the first filtration bed, the second filtration bed comprising a second granular and/or angular media, the second granular and/or angular media having a second amount of surface area per volume of the second filtration media, the second amount of surface area being less than the first amount of surface area; 
 wherein the at least one inlet comprises:
 an influent inlet by which the water or wastewater enters the vessel; 
 a carbon source inlet by which a carbon source is introduced into the system to support removal of nitrates in the water or wastewater by microorganisms present in the first granular and/or angular media; and 
 a backwash inlet by which a water only backwash is introduced to the system, the water only backwash removing at least a majority of nitrogen bubbles trapped in interstices of the first or second filtration bed; 
 
 wherein the water or wastewater enters the system via the influent inlet, flows through the first filtration bed and the second filtration bed, and exits the vessel through the at least one outlet. 
 
     
     
       2. The system of  claim 1 , wherein the first granular and/or angular media ranges in size from 0.1 millimeter to 3 millimeters. 
     
     
       3. The system of  claim 1 , wherein the first granular and/or angular media is comprised of expanded clay or shale, and/or plastic. 
     
     
       4. The system of  claim 1 , wherein the first granular and/or angular media is comprised of a blend of different materials. 
     
     
       5. The system of  claim 1 , wherein the second granular and/or angular media comprises sand having a particle size between 0.1 millimeters to 10 millimeters and a density greater than 1,500 kg/m 3 . 
     
     
       6. The system of  claim 5 , wherein the sand has a particle size between 0.5 millimeters and 2.5 millimeters. 
     
     
       7. The system of  claim 1 , further comprising a third filtration bed, the third filtration bed supporting the second filtration bed and comprising a third granular and/or angular media. 
     
     
       8. The system of  claim 7 , wherein the third granular and/or angular media is gravel with a particle size between 2 millimeters to 50 millimeters. 
     
     
       9. The system of  claim 1 , wherein the first filtration bed supports microorganisms for removing nitrates from the water or wastewater, and wherein the second filtration bed assists in suspended solid capture from the water or wastewater. 
     
     
       10. The system of  claim 1 , wherein the carbon source introduced into the system is methanol, used to assist microorganisms present in the first or second filtration bed in removing nitrates from the water or wastewater. 
     
     
       11. The system of  claim 1 , wherein the water or wastewater passes through the system due to external forces, the external forces comprising gravity. 
     
     
       12. The system of  claim 11 , wherein the external forces additionally comprise pressurization. 
     
     
       13. A down flow water or wastewater treatment system for removing nitrates from water or wastewater, the system comprising:
 an influent inlet for receiving water or wastewater from a source outside of the treatment system; 
 a vessel for containing the water or wastewater, the vessel comprising:
 a first filtration bed comprised of a first filtration media having a first amount of surface area per volume of the first filtration media, the surface area of the first filtration media configured for biological and physical treatment of the water or wastewater; 
 a second filtration bed comprised of a second filtration media having a second amount of surface area per volume of the second filtration media, the second amount of surface area being less than the first amount of surface area, the second filtration bed supporting the first filtration bed; and 
 a support bed, the support bed supporting the second filtration bed; 
 one or more nozzles providing fluid communication between the vessel area adjacent to the support bed and the system outlet, the nozzles providing an exit for effluent after traveling through the vessel; 
 
 an effluent outlet, for removing treated water or wastewater from the system; 
 one or more inlets for the introduction of air scour and water only backwash into the vessel, the inlets providing air scour and backwash water through the nozzles into the support bed, into the second filtration bed, and subsequently into the first filtration bed, the water only backwash removing at least a majority of nitrogen bubbles trapped in interstices of the first or second filtration bed; and 
 a carbon source inlet by which a carbon source is introduced into the system in order to support removal of nitrates in the water or wastewater by microorganisms present in the first filtration media. 
 
     
     
       14. The system of  claim 13 , wherein the first filtration bed comprises 50%-89% of the depth of the combined first filtration bed and second filtration bed. 
     
     
       15. The system of  claim 13 , wherein the first filtration media is comprised of expanded clay, shale, plastic and/or fiber material. 
     
     
       16. The system of  claim 13 , wherein the first filtration media is comprised of a blend of different materials. 
     
     
       17. The system of  claim 13 , wherein the first filtration media comprises a material specifically configured with sufficient surface area to support microorganisms for nitrate removal.